Performance of Transgenic Tomatoes Expressing Cucumber Mosaic Virus CP Gene under Epidemic Conditions

Abstract

Three processing tomato (Lycopersicon esculentum Mill.) lines engineered to express the cucumber mosaic virus (CMV) capsid protein (CP) gene were evaluated in the summers of 1995 and 1996 under high levels of naturally occurring CMV disease pressure. One tomato line expressed the capsid protein gene from a subgroup II isolate of CMV (line 11527), whereas two lines (12261 and 12295) expressed the capsid protein genes from a CMV subgroup I and a subgroup II isolate. Evaluation of CMV incidence based on symptomatic plants revealed that only 9% and 8% of the plants in line 11527 were infected in 1995 and 1996, respectively, 5 weeks after being transplanted. None of the plants in line 12261 developed symptoms in 1995, whereas 26% were symptomatic in 1996. There were no symptomatic plants in line 12295 in either the 1995 or the 1996 trial. In contrast to the CMV transgenic lines, 96% and 95% of the susceptible control plants were symptomatic by the 5-week rating period. CMV incidence in the CMV transgenic lines was much higher when infection was based on detection of virus by enzyme-linked immunosorbent assay (ELISA). This was particularly true in the 1996 trial where no less than 97% of the plants within a treatment were determined to be infected. Though a relatively high percentage of the transgenic plants were infected, the amount of CMV that accumulated in these plants was significantly less than in the susceptible controls, which may explain the occurrence of the attenuated symptoms. Despite CMV infection of the transgenic lines in the Alabama field trials, the performance of these lines could be of practical value to growers.